Worm rotary compressors with liquid joints



April 1965 B. ZIMMERN 3,180,565

WORM ROTARY COMPRESSORS WITH LIQUID JOINTS Filed ma 6, 1963 4 Sheets-Sheet 1 BERNARD Z\MMERN mhmwmumm April 1965 B. ZIMMERN 3,180,565

Filed llay 6, 1965 ROTARY OOMRBESSORS WITH LIQUID JOINTS 4 Sheets-Sheet 2 April 27, 1965 s. ZIMMERN WORM ROTARY COMJPRESSORS WITH LIQUID JOINTS 4 sheets-sheet 3 Filed May 6, 1963 N m. MK Z hm o M mm T Kn L wa m n 13 1M 1! 1}! I 2 8 a 3 /L S ,I.. W9 mm K 0 0: 3 0mm No .5-

April 1965 B. ZIMMERN 3,180,565

WORM ROTARY COMPHESSORS WITH LIQUID JOINTS Filed May 6, 1963 4 Sheets-Sheet 4 Inve n+or BERuARv ZMM an United States Patent 3,180,565 WORM ROTARY CDMPRESSORS WITH LIQUID JOINTS Bernard Zimmern, 27 Rue Delabordere, Neuilly-sur-eine, France Filed May 6, 1963, Ser. No. 278,125 Claims priority, application France, May 8, 1962, 896,859, Patent 1,331,998 18 Claims. (Cl. 230-150) The present invention concerns various improvements relating to rotary compressors utilizing hour-glass worms as drive members and in which the tightness between the worm threads and the pinion teeth is ensured by liquid joints, the said improvements making it possible, in particular, to' produce compressors having an appreciable eitective volume corresponding to a reduced number of Worm threads and aifording nevertheless a high compression rate per stage, whilst using hour-glass worms and pinions made in one piece.

The inventor has noticed in fact that in order to obtain an important effective volume between the threads of such of a screw, without having to split either the screw or the pinions into several pieces and assemble thosetwo types of components by successive segments, it'becomes necessary to resort to worms having but four to six threads, and capable of cooperating with unitary pinions having preferably seven or eleven teeth respectively.

The present description will show the means whereby the inventor can successfully obtain in a single stage, a

pressure of 7 kg./cm. for current industrial uses, in spite of the above-mentioned; reduced number of threads.

Another improvement within the'scope of the present invention concerns the relative forms to be given to the worm extension on the high pressure side, as well as to the surrounding casing, in order to eliminate all axial thrusts on the worm and make it possible'for the compressor bearings to rotate at a high speed, so as to obtain the highest possible power to weight ratio.

The inventor has noticed that when it is desired to obtain with only four threads the high compression rate required to produce the above-mentioned pressure of 7 kg./cm. it becomes necessary to combine three means which the known art has used either separately or in'pairs and to provide simultaneously, between the compressed gas inlet and outlet, a reduction in the length of the compression chambers defined by adjacent threads, a

reduction in the depth of Worm threads, and a reduction in the diameter of the casing surrounding said worm.

It is possible, theoretically at least, to combine these three means, by giving to the casing surrounding the worm a curvature having the same direction as that of the worm, together with asuitable offset, but the rectilinear path of liquid particles injected in a direction tangential -to the casing at one end of the latter-in order to form the said liquid joints, produces normally a break in continuity within these joints.

For that reason, and quite independently from the known cylindrical shape, the inventor advocates, as a means of avoiding said breaks in continuity and simplitying the construction of compressors, the use of casings having a linear profile in cross-section, i.e. conical casings producing a compression rate which increases in proportion to the angle of opening of the cone, 'thesaid casings becoming at the extreme limit, for an angle of opening of 180,plarie-shaped casings cooperating with discs carrying spirally shaped threads, and placed at right angles to the casing axis.

It is possible to accomplish in practice the required aim and to produce a 7 kg./cm. pressure in a single stage and with one-piece drive members, by using a cylindrical casing, provided that the worm contains six "ice threads, whereas with four threads only it becomes necessary to combine all three above mentioned means, and to use preferably plane-shaped casings.

Other objects of the present invention will appear from the following description, to be read in conjunction with the annexed drawings, in connection with various embodiments of compressors according to the invention, it being understood that said embodiments are given as examples only.

On the drawings:

FIGURE 1 shows diagrammatically a diametral cross section .of an ordinary hour-glass worm mounting, indicating the shape ordinarily given to the teeth of a unitary pinion in order to enable them to be inserted between the threads of a unitary 'globoid worm, the delivery rate of compressed gas being very low with this type of mounting.

FIGURE 2 shows one half of a diametral cross section of a compressor having a higher rate of delivery, with a unitary six thread hour-glass worm cooperating with a truncated cone shaped casing together with two unitary pinions having eleven teeth.

FIGURE 3 shows one half of a cross section similar to FIGURE 2, but relates to a compressor with a unitary four thread hour-glass worm cooperating with two unitary pinions of seven teeth.

positions of the worm and pinions.

7 of the compressor of FIGURE 6, with the casing cu away along line VIIVII of said FIGURE6.

FIGURE 1 shows hour-glass worm 1, truncated at its upper and lower portions according to conical profiles 2 and 3, and cooperating with a pinion 4 having fifteen teeth adapted to engage 'with the threads of said worm.

Worm 1 has a circular outer profile, corresponding to chain dotted circle 5, the latter being concentric with circle 6 which corresponds to the bottom of the threads in worm 1.

It will be understood, by inspecting the position shown on FIGURE 1, that the three pinion teeth 7, 8 and 9, can easily be inserted between threads 10, 11, 12 and 13 in worm 1, which makes it possible to use a unitary worm and a unitary pinion, and to avoid having to split either the wormor the pinionsinto severalpieces which would require to be assembled in successive stages, in step with the insertion of said pinion teeth betweenthe threads of said worm.

In this embodiment, the required result is obtained by reason of the fact that the faces '14 and 15- in threads worm and'pinion s can be either made in one piece or formed by assembling several segments into'one piece prior to inserting the pinion teeth within the worm threads.

However, one disadvantage in this arrangement stems from the fact that the volume between adjacent threads is very reduced, which results in a rather low value of delivery rate and power to weight ratio.

It will be readily understood that the effective volume in the compression chambers increases appreciably when providing a much reduced taper on the pinion teeth, in which case the use of unitary components, becomes possible only by reducing the number of threads, the compression rate thereby obtained being entirely insufiicient in known types of compressors.

FIGURE 2, shows the hour-glass worm .10, whose top portion is truncated according to conical profileindicated in 2a, and whose eifective outer profile is also conical as may be seen in 5a, on said figure. Theroots of the threads define a concave portion of the worm surface which is part circular when seen in axial section.

It will be seen on FIGURE 2 that the compression chambers contained between adjacent threads decrease progressively in cross section, towardsthe end of compression, particularly owing to the fact that, starting from point 16 level, the depth of threads decreases gradually, in such a way that the truncation, indicated by 17 on thread 18, progressively increases down to the base of the effective part in the worm, i.e. down to'point l9.

Theworm extends in 2%, beyond said effective part,

said extension corresponding in shape to the profile of the conical casing which surrounds it.

' It will further be seen on FIGURE 2 that the conical Cir shape 5a tends to make up for the increase in diameter at the bottom of the worm, below the median plane of said worm, and that the centre of gravity of the compression chambers tends, at the end of compression, to take upa position, such as that of point 19, which is nearer to the worm axis thanwould be the case if the'worm co- 1 operated with cylindrical casings.

Therefore, as mentioned above, a combination of the three means enumerated in the introduction to the prescut description, results in the production of a compression rate equal to or even higher than that of the compressor shown on FIGURE. 1, but with a much higher volume of delivery, whilst afifording the possibility of using unitary pinions and worm having relative profiles enabling them to be assembled for given suitable angular positions of worm 1a.

Indeed, since the said worm is truncated on line 2a,.

there are no threads above pinion tooth 21; therefore tooth 21 can easily penetrate between thread 23 and worm top portion 22. v

Median tooth 24 in the eifective sector of said pinion can therefore penetrate easily between threads 18 and 23, owing to the fact that sides 25 and 26 respectively associated to threads 23 and 18, adapted to cooperate on chambers contained by the casings and the worm, as a result of the reduced number of threads.

Besides, in the arrangement of FIGURE 3, the sides of adjacent worm threads may be made to converge outwardly, since it becomes possible to place pinion 29 in a position wherein, as in the case shown in cross section on -FIGURE 3, there ison worm 1b but one thread 30 requiring to be engaged with two adjacent teeth 31 and 32 on pinion 29 ,said thread beingevenable to have in cross section any convex shape capable of being-easily inserted between said teeth 31 and 32 on pinion 29.

It will be readily understood that the placing of pinion 29 on the worm could become impossible if there were, opposite the said worm, two adjacent threads defined by sides converging towards the centre of the said piston.

However, owing to the reduction'from' six to four in the number of threads, the production of a compression rate comparabletothat of the-compressor on FIGURE 2 makes it necessary to appreciably increase the reduction in diameter, i.e.toincrease appreciably the slope of profile 33 relatively to the vertical, and to go even as far as using plane-shapedcasings placed at right angles to the worm axis.

In practice, it will be preferable to use either a six thread cylindrical worm, or a four thread worm, cooperating with plane-shaped casings, in order to produce compression rate valuesof aboutS.

When using the said plane-shaped casings, it is advantageous to provide two compressors using respectively two symmetrical threads associated to one double worm, in order to balance the axial thrusts exerted by the gases in the said compressors on the spindle; of said double worm. The arrangementon FIGURE 4 concerns a compressor in which worm 1c, having a cylindrical profile on the major part'of its height, is truncated in'Zb, at its top portion, for suction.

This figure shows how it is possible to avoidthe production by the: compressed gases of an upward. axial thrust on the, lower face of a vertically placed worm having a cylindrical outer profile, and consequently to relieve the bearings, so as to make it possible to increase the rotational speed and thepower to weight ratio of the compressor, taking into account the fact that the worm isnot subjected toradial thrusts, since the compressor is provided with pinions mounted in pairs.

The-worm 1c in FIGURE 4 comprises beyond its effective portion, i.e..beyond point 191:, a cylindrical extension 29a.

can be carried out simply by bringing two of the six worm threads opposite one pinion, in a position approximately symmetrical to the median plane of constriction of said worm, and by giving parallel profiles, seen particularly in 25 and 26, to the sides of adjacent worm threads, so as to enable them to cooperate with pinion teeth having also parallel sides.

It will be seen that the number of teeth which have to The compressor in FIGURE 4 is of a known type, but includes however, in its lower portion, an exhaust groove which communicates with the open air by means of a duct, diagrammatically. shown in 35,,the .said groove affordingthe possibility'to eliminate all pressures on the lower face of the worm, and to reinjectthe leaking. liquid recovered within said groove 35 in the direction of arrows 36.

It will be understood that the liquid in the joints can penetrate between the. worm and the casings below point 1%, and accumulate within exhaust groove. 34, which makes it necessary to provide, below worm 10, a circular segment 37, forming a plane joint, said segment resting on at least onespring 38 in order to protect the roller bearings carrying the spindle 8 of worm 1c.

Since this exhaust groove communicates with the open air there is no possibility of water infiltrating between the worm base and the casing and accumulating under pres sure beneath the worm in a manner liable to produce an upward axial thrust. 1 e

The compressor shown on FIGURE 5 includes worm 10 having a cylindrical outer profile, as well as an exhaust groove 34 communicating with the suction side by means of a duct 35, asin the case of FIGURE 4. The roots of the threads define a concave portion of the worm surface which is part circular when seen in axial section.

The worm has six threads, and it will be seen that both pinions 39 and 40 are provided with eleven teeth having two parallel sides and similar in type to those shown on FIGURE 2.

Taking into account the injection of liquid, the effective compression rate in a compressor of this kind is in fact slightly higher than the theoretical rate. It may range from 5.5 to 6, whereas its theoretical value is between 4 and 5, which makes it possible to produce compressed air at a 7 kg./cm. pressure, with a good efficiency factor.

The figure shows in 41 an exhaust port, outlined in.

dotted lines and formed within the casing thickness, said port being placed infact in front of the plan of FIG- URE 5.

The position in height of worm 10 can be adjusted by means of threaded plug 42.

It will be seen further that worm 1c is mounted between casing 43 and cap 44, by means of lower bearing 45 and upper bearing 46, lower bearing 45 resting on a spring washer 47 and both bearings being protected from all contact with the liquid in the joints by means of circumferential gaskets 48 and 49 respectively.

Pinion 39, made in a plastic substance, is mountedon a steel support. I

An inspection of the embodiment of compressors shown on FIGURES 6 and 7 will reveal that the disc shaped drive member 1e is provided with threads on surfaces perpendicular. to the axis of the compressor. The roots The spindle carrying the disc 1e is mounted on covers 54 and 55 by means of bearings 45a and 46a which are protected against water infiltration by means of plane shaped gaskets 3701' and 37b, loaded by springs 38:: and 38b. Y

The assembly-of said drive member includes in the lower part a washer 47a and a tightening screw 69.

This assembly includes in the upper part two screws 42a. A lubricator cap 70 is provided for lubricating bearing 46a.

It will be seen in FIGURE 7 that the compressed air outlet duct 60 is made up in fact by bringing together two ducts '71 and 72 which receive respectively the compressed air in the vicinity of upper pinions 62 and 63.

Similarly, the lower duct 61 is made up of two ducts 73 and 74 brought together. A portion of duct 73 has been taken away in order to show that the said duct receives compressed air at the level of the lower left pinion, not

shown on the drawing, whereas duct 74 receives compressed air at the level of pinion 64.

of these threads define concave surface portions in the form ofannular depressions which are coaxial with the axis of said compressor and part circular in a plane containing said axis.

The portion of FIGURE 6 in which the casingis shown broken away shows in cross section one of the effective portions of the compressor, indicated by 51, wherein the threads are spiral shaped, and not helix shaped as usual, the depth of said threads increasing gradually from point 52 up to the median portion corresponding substantially to the position of thread 51, and decreasing beyond that position towards the periphery of the disc, i.e.

. in the direction of point 53.

The disc includes. two spiral threads symmetrically placed relatively to the median plane of the compressor and situated respectively one on the top of the disc/the other on the bottom.

The crests of the threads on the disc bear upon two plane shaped caps 54 and 55 provided respectively above and below the disc and including internal bosses 56 and 57. '1 i Gas entering the compressor periphery by way of piping 58 becomes graduallycompressed towards the interior of the compressor, i.e. in the vicinity of spindle 59 of disc 1e. This air escapes at bottom and at top by way of duct 60 and 61 which may thereafter converge within a compressed air manifold.

As mentioned above, the decrease in diameter of the compressor from the inlet of gases to their outlet in the vicinity of the spindle, acting in combination With the gradual reduction in the depth of threads provided immediately beyond the position shown in FIGURE 6, and with the gradual reduction in the length of compression chambers, is operative in producing a high compression rate of about 5.

By combining these three means, it is possible to obtain a pressure of at least 7 kg./cm. as in the case of the cylindrical compressor of FIGURE 5, by using drive members with only four threads, instead of the six threads used in the case of FIGURE 5..

The compressor in FIGURE 6 has four pinions, three of which are indicated on the drawing by the numerals 62, 63 and 64.

The liquid which is intended to ensure the tightness A grease box a is also provided in the lower portion of spindle 59 for lubricating bearing 45a.

The edge in the sectionedpart 58 of cover 55 corresponds to one of the millings provided to secure a clearance for the various pinions. The casing on which bear the two covers 54 and 55 can be seen on the drawing, in particular at76. This casing whose outer shape is formed by a surface of revolution has an internal dissymmetry and forms a suction volute before joining up with the suction in the straight portion of the drawing.

The mounting of pinion 62 can also be seen in FIG- URE 7, with its steel support indicated under the numeral Said pinion and support are mounted on one of the shafts 78 by means of a spring'washer 79 and a screw 80a which fulfils the same function as screw 80 seen in FIGURE 5. The truncated ridges of three out of the four threads in disc 12 are indicated respectively by numerals 81, 82 and 83, the sides of said threads being indicated respectively by numerals 81a, 82a, 82b and 83b, and the truncated peripheral portions of said'threads being indicated by numeral 2d.

The dotted line indicated by numeral 84 shows the shape given to a compressed air exhaust port leading through'cover 54 and opening into duct 71 by means of outlet 85.

For the sake of simplicity, the casings surroundings the pinions and serving to recover leaking fluids, have been omitted from the drawing.

It is to be clearly understood that the embodiments referred to in the above description have been given by way of an example only, and that they may include various amendments, alterations or improvements without departing from either the scope or the spirit of the present invention.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. A compressor comprising a casing having a central axis, a disc rotatably and coaxially mounted in said casing, atleast one face of said disc being formed with a coaxial annular depression therein, said depression being partcircular in section, a plurality of spirally extending threads projecting upwardly from said depression to the level of the remainder of said disc surface, the inner surface of said casing comprising a portion positioned to be swept by side carries four threads, with not less than two nor more than three of said threads meshing with each pinion at.

any one time. 7 4. A compressor as claimed in claim 3 in which each pinion carries seven teeth.

5. A compressor as claimed in claim 4 in which said threads mesh with said pinions over an arc of about 102".

6. A compressor comprising a casing having a central axis, a one-piece drive member rotatably and coaxially mounted in said casing, said'drive member having at least one concave surface portion which defines a pair of circular arcs in those planes containing said axis, a group of screw threads positioned on said concave surface, the crests of said threads lying in the locus generated by a straight line rotated about a point on said axis, at least part of the inner surface of said casing being positioned to be swept by said crests and define therewith a plurality of pressure chambers extending from one end'of said group of screw threads to the other, a plurality of toothed pinions mounted to turn about axes perpendicular to the axis of said drive/member and projecting through said casing to mesh with said threads, each thread traversing.

an are about the axis of the drive emember no greater than that between adjacent pinions, a low pressure fluid inlet in said casing communicating with one end of said group of threads and a plurality of high pressure fiuid outlets in said casing, one immediately adjacent each of said pinions and communicating with the other end of said group, the teeth on said pinion being thicker in said axial planes than said threads, and at least two but not more I than three teeth of each pinion meshing simultaneously with said threads, and blocking at least one of said pres sure chambers.

7. A compressor as claimed in claim 6 in which said drive member terminates near the inlet end of the thread group in a surface transverse to said locus, and said transverse surface terminates where it meets said locusinia chamfer defining one wall of a passageway communicate ing withsaid inlet.

8. A compressor as claimed in claim 7 in which said drive member carries six discrete threads and there are two of said pinions, the two flanks of each tooth on said pinions being parallel to each other.

9. A compressor as claimed in claim 8 in which each pinion has eleven teeth.

10. A compressor as claimed in claim 7 in which said drive member carries four discrete threads and there are two of said pinions, and in which the two flanks of each pinion tooth converge as they approach the center of the.

pinion on which that tooth is carried.

11. A-compressor as claimed in claim 10 in which each .2 taining said axis and provided with a group of said threads having their crests in a plane which constitutes the locus generated by said straight line, said disc being formed with a peripheral edge transverse tosaid one face positioned near the inlet end of 'saidthread group, and. said edge terminating whereit meets said one face in a chamfer defining one wall of'a passage which communicates with said inlet.

14. A compressor as claimed'in claim 13 comprising a single drive member having two oppositely facing concave surface portions, eachofwhich defines a circular arc in those planes containing said axis, and is provided with a group of said threads with the crests of, the threads posi tioned onsaid two concave surface portions lying in the loci generated by twoparailel lines perpendicular to said axis which are rotated thereabout, and a pair of pinions engaging the threads on each ofcsaid. concave surface portions. i

15. A compressor. as claimed 'in'claim 14 in' which there are four discrete threads on each concave surface portion and the two fianks of each pinion tooth converge as they approach the center of the pinion on which that tooth is carried. p

16. A compressor as claimed in'c1aim6 in which said straight line isperpendicular to said axis ar'rdthe inner surface of said casing forms a gas suction volute.

17. A compressor asclaimed in claim 6 in which said straight 'line is parallel to said central axis,'said drive member carries six discrete threads, and each pinion carries eleven teeth. V

18.. .A compressor'as claimed in claim 17 comprising means-for supplying atthe inlet end of said casing sealing fluid which flows between said drive member and pinions, said casing terminating at its outlet, end in a reservoir positioned to receive said sealing fluid after it has passed between sa'id" drive member and pinions, saidreservoir being connected to said inlet end of said casing and said drive member comprising a thread-free cylindrical portion extending into said reservoir. 1

References Cited the Examiner UNITED STATES. PATENTS KARL J. ALBRECHT, Primary Examiner.

WILBUR I. GGODLIN, JQSEPH H. BRANSON, JR.,

' I Examiners. 

1. A COMPRESSOR COMPRISING A CASING HAVING A CENTRAL AXIS, A DISC ROTATABLY AND COAXIALLY MOUNTED IN SAID CASING, AT LEAST ONE FACE OF SAID DISC BEING FORMED WITH A COAXIAL CANNULAR DEPRESSION THEREIN, SAID DEPRESSION BEING PARTCIRCULAR IN SECTION, A PLURALITY OF SPIRALLY EXTENDING THREADS PROJECTING UPWARDLY FROM SAID DEPRESSION TO THE LEVEL OF THE REMAINDER OF SAID DISC SURFACE, THE INNER SURFACE OF SAID CASING COMPRISING A PORTION POSITIONED TO BE SWEPT BY SAID THREADS AND DEFINE THEREWITH A PLURALITY OF COMPRESSION CHAMBERS, FLUID INLET MEANS IN SAID CASING ADJACENT THE PERIPHERY OF SAID DISC AND FLUID OUTLET MEANS IN SAID CASING NEAR THE CENTER OF SAID DISC, AND AT LEAST ONE PINION 